The smallest frontosa I have for holding eggs is 3.5".
I am almost sure your frontosa is not holding. She/he could be holding air during the transport or introducing it to a new tank. It happens quite often with the new fish. Check to see if you can see eggs in its mouth. Another easy way to tell is: 1) frontosa holding eggs will swim and stay normal position. 2) frontosa holding air in its mouth will slightly pointing down trying not to let the air bubble escape.
I am almost sure your frontosa is not holding. She/he could be holding air during the transport or introducing it to a new tank. It happens quite often with the new fish. Check to see if you can see eggs in its mouth. Another easy way to tell is: 1) frontosa holding eggs will swim and stay normal position. 2) frontosa holding air in its mouth will slightly pointing down trying not to let the air bubble escape.